s= 'Python is an easy to learn, powerful programming language. It has efficient high-level data structures and a simple but effective approach to object-oriented programming.'
dct={ }      # 统计结果类似 {'p':21, 'a':5,  'x':2}
for  c   in  s.lower():
    dct[c]=dct.get(c,0) + 1
print(dct) 